1. Field of the Invention
The present invention relates to a reflective screen.
2. Description of the Related Art
Reflective screens having the reflection property of reflecting light from projectors and the diffusion property of diffusing reflected light are used as screens for projectors such as OHP (Over Head Projectors), slides, motion picture projectors, and the like. The most general screen includes a laminate of a black backing sheet and a white poly(vinyl chloride) sheet used as a light reflecting base material. There have also been used reflective screens each including a light reflecting base material and a reflecting layer formed thereon by coating white ink containing a pearl pigment or an aluminum paste pigment, the screens being further roughened by micro processing to improve reflectance. However, in these screens, consideration has not been not given to improvement in the contrast ratio between a black dark picture portion and a white bright picture portion, and thus use of the screens have been limited to use in darkrooms in order to achieve clear images.
Accordingly, there has been proposed a reflective screen improved in contrast ratio to achieve clear images even in environments in which illuminating light from a ceiling and light from a window are present. An example of the proposed screen is one in which an eaves including a light-absorbing material called a “glaze” is provided for preventing absorption of projector light incident from the front side, but external light at an incidence angle is absorbed (refer to, for example, Japanese Unexamined Patent Application Publication No. 10-39418). There has also been proposed a screen in which a black fibrous material is used for a light absorbing layer, for achieving the same effect as the eaves (refer to, for example, Japanese Unexamined Patent Application Publication No. 10-282577).
There has been further disclosed a screen in which a geometrical relation between a Fresnel lens shape, the screen, and an observer is controlled to avoid reflected light of external light incident from above from entering the eyes of the observer (refer to, for example, Japanese Patent No. 3655972).
There has been further disclosed a screen in which the inclined surface of a Fresnel lens is used as a reflecting surface, and a rack surface is used as a light absorbing surface, thereby improving contrast even under external light (refer to, for example, Japanese Patent Nos. 2976148 and 2984801).